Exhaust gas mass flow sensors comprise a supporting body of parallelepiped shape, for example, onto which a heating element is applied, e.g. in the form of a conductor path. Typically, a holding element is used to fasten the supporting body in an exhaust gas channel such that the short side of the supporting body is flown to by the exhaust gas mass flow and the exhaust gas mass flow flows along the long side of the supporting body. Heat transfer from the heating element to the exhaust gas mass flow takes place especially by convection. By measuring the change in temperature or by measuring the power input required to maintain the temperatures of the heating element constant, an exhaust gas mass flow can be determined using suitable algorithms. To achieve this, a temperature sensor is possibly arranged upstream of the exhaust gas mass flow sensor in the flow direction, the sensor measuring the temperature. The temperature sensor can be identical in structure to the exhaust gas mass flow sensor, the heating element here being used only to measure the temperature.
To the present day, using exhaust gas mass flow sensors in exhaust gas mass flows of motor vehicles has been possible only to a very limited extent. The reasons for this are the high temperatures occurring, as well as the particles contained in the exhaust gas flow of motor vehicles that cause deposits on the exhaust gas mass flow sensor. This leads to a corruption of the measurement results and thus to an inaccurate determination of the exhaust gas mass flow. The occurrence of condensates or of liquid droplets in the exhaust gas mass flow that contact the supporting body of the exhaust gas mass flow sensor and condense or evaporate there cause a significant corruption of the measurement results.